Installing Offy heads

[chiefdave]

There is so much info on installing aluminum heads that I am a little overloaded. So far I've gathered up the heads, permatex aviation sealer and Fel Pro non copper gaskets.


Most recommend using a spay sealer on both sides of the head gaskets. I've always installed head gaskets dry. What would be the advantage of using the sealer?


Torque recommendations are all over the place. Would 45 be OK in steps of 15/30/45?


With the increased compression would a step or two colder plugs be in order? A little extra timing advance?


This would be a good time to change thermostats. Given the advances in coolant over the last 70 years would 180's be suitable for year round use.


Finally could someone go over checking piston to head clearance? The block was decked during rebuild but the build sheet didn't specify how much metal was removed.


Thanks in advance for any help, Dave.

 

[marko39]

I would not use the sealer as the next time you have to pull the heads it will be a sob. Grease would be better but. I don't think you need anything as long as both surfaces are clean and flat.

 

[tubman]

I only use grease when installing heads. It allows them to move around a bit and conform to the block. Sealer is OK until the next time you have to remove the heads and old gaskets.

If you are installing new Offenhauser heads, you will probably find that the bolt holes are quite large compared to the bolts/studs. Offenhauser has done this to make them easier to remove if studs are used. This means they can move around a bit during installation, which may be a problem. The best thing to do with them is to have alignment pins installed in the block with corresponding holes in the head. "GOSFAST" on here does this to all the engines he builds with good results. If you already have the engine ready to go, you can still do something to stabilize the heads. Here is a link to a thread showing what I do in such a situation : https://www.fordbarn.com/forum/showthread.php?t=230469&highlight=tube.

Your torque sequence seems fine. Remember to do it with the engine cool and repeat the last figure until the torque is stabilized. Three times probably won't do it.

I'd run plugs with the same heat range as stock to start with. If there are problems down the road, you can address it then. Remember, stock plugs are too short to be used in aluminum aftermarket heads. The aluminum heads have deeper threads and use longer plugs. I think "L -series Champions are the right length, but the plug numbering systems have changed so much that you can't be sure. The best thing is to go to your FLAPS and try to find plugs that fit correctly. Finding the right plugs can be a pain sometimes.

As to thermostats, I would run the 180's. Running an engine too cold is almost as bad as running one too hot. Thermostats have nothing to do with how hot and engine runs, just when they open up to allow coolant flow.

Finally, you are smart to be looking at piston clearance. I believe it is the single most effective thing you can do to make a flathead more efficient. You should shoot for .045- .050 clearance. There are a lot of threads around about how to check this with clay or aluminum foil balls. (I like the latter.) Even with new aftermarket cylinder heads, you may have to make a trip to the machine shop to get the heads close. On the last set of used Edmunds heads I used, I had to take .015 off of one head and .025 off the other to get close. It then took just a little cleaning up with a die grinder to get them perfect.

Good luck with your endeavor.

 

[GOSFAST]

There is so much info on installing aluminum heads that I am a little overloaded. So far I've gathered up the heads, permatex aviation sealer and Fel Pro non copper gaskets.


Most recommend using a spay sealer on both sides of the head gaskets. I've always installed head gaskets dry. What would be the advantage of using the sealer?


Torque recommendations are all over the place. Would 45 be OK in steps of 15/30/45?


With the increased compression would a step or two colder plugs be in order? A little extra timing advance?


This would be a good time to change thermostats. Given the advances in coolant over the last 70 years would 180's be suitable for year round use.


Finally could someone go over checking piston to head clearance? The block was decked during rebuild but the build sheet didn't specify how much metal was removed.


Thanks in advance for any help, Dave.

Hi Dave, just a tip, but before you install those heads make certain the spark plugs you intend to use will fit at the correct depth, been down this road many times with these aftermarket pieces. We actually made spacers (shims) to raise the plugs if necessary.

You don't want any threads "hanging' in the cylinders. Also, when it comes time to change the plugs (with aluminum heads) make sure the unit is "cold"!

Thanks, Gary in N.Y.

P.S. With respect to using sealer on the head gaskets, just about all "composite" gaskets get installed "dry", no "coating" on the gaskets is needed. Most times we use the Fel-Pro line here but more recently we will be trying the "Best" line??

 

[Bored&Stroked]

Tips:

a) Use no sealer on those gaskets - makes it all the harder to get the heads off at a later date
b) Use a good quality stud sealer on the coarse threads of the studs or bolts. If using studs, then use ARP thread lubricants on the fine threads - to get accurate torque readings. I usually torque aluminum heads to 55 lbs. Start at 30 - 35 lbs - do three sequences. After the engine is started and gets warm - you'll find the torque will change. Heat cycle the engine a few times - checking torque when it is cool.

Quality of fasteners is key! Use good thick and hardened washers on the top side (to not score the aluminum). If you can afford it - buy a new set of ARP fasteners for the job - they don't stretch and torque readings are more consistent. Note - if using studs, the ARP ones have a hex/allen head female receiver in the tops - makes it easy to remove the studs from the top (with the head on) - one at a time. You'll be happy you have them if you are going studs! (Makes head removal a breeze).

c) Put anti-seize on the sides of all studs/bolts - helps with pulling the heads later.
d) Check piston to head clearance on BOTH sides (it is usually different). Shoot for .040 clearance - don't go closer than that. Also check for piston dome conformity to the head dome - there are at least two very different piston dome shapes - one is a perfect arc (like Ross pistons), others are more elliptical in nature - causing different clearances on different parts of the domes (most heads have a single uniform dome shape).
e) I use the 'Best' line of gaskets if going composite - though on my last guild I used Cometic MLS gaskets. Keep in mind, that MLS gaskets usually require a very smooth deck/head surface finish - so you can't just use them on everything.
f) If you have the engine at the machine shop, you might consider having the deck height checked on both sides. You'll usually find that it is different side-to-side, so if you are decking the block, you want to true up the compression heights to be the same. BUT - you have to also know your quench/clearance with the associated heads you're using - so it is a situation where ALL the parts need to be in hand . . .
g) Heads can be 're-domed' if necessary - but few shops have the tools.

If your heads are used, you may already not have enough dome left to do what was described above. If your heads are used, you might want to attach some pictures of your head bottoms - I can tell by looking at them.

h) I prefer to not use Champion plugs - have had too many issues with them fouling. I tend to use NGK plugs the most - in a '6' heat range. Do as Gary noted - don't have any thread hanging down into the combustion chamber.

I) Depending on the cam selection, you may also need to check for valve to head clearances - I usually want .060 minimum . . . the area of most concern is the TOP eyebrow area of the valve pockets (in the heads). The valves are angled, so this is where they will be closest to the head valve pockets.

Good luck!
B&S

 

[chiefdave]

Tips:

f) If you have the engine at the machine shop, you might consider having the deck height checked on both sides.

If your heads are used, you may already not have enough dome left to do what was described above. If your heads are used, you might want to attach some pictures of your head bottoms - I can tell by looking at them.

I) Depending on the cam selection, you may also need to check for valve to head clearances - I usually want .060 minimum . . . the area of most concern is the TOP eyebrow area of the valve pockets (in the heads). The valves are angled, so this is where they will be closest to the head valve pockets.

Good luck!
B&S

Could not get pictures to upload but the heads are used. . Depth of the domes is around .174". To me it looks like the valve pockets have been cut for clearance when compared to a new head. The car is an older restoration and the engine was rebuilt in 2003 with very few miles since. It came with a lot of paperwork including a detailed build sheet for the engine. The block was decked, pistons used were 8BA-6108-S30, new head bolts, PF494 hard washers and a cam of unknown grind (just a slight lope at idle).
To make sure I have the procedure right place 2 marble size balls of aluminum foil at the bottom of the piston and possibly one in the center held in place with a dab of grease. Install head with a new gasket and snug with a few head bolt then turn engine by hand one full revolution. Measure the flattened balls and use the thinnest as your datum. Subtract .040 from this figure and subtract another .010 for gasket compression when fully torqued. The resulting figure would be the maximum the heads can be milled?

 

[supereal]

If the heads are not new, have a good machine shop check them, and resurface if necessary. We find that many aluminum heads are warped enough to cause problems. Check each spark plug hole threads, and have Heli-Coils or adapters used if necessary.

 

[Bored&Stroked]

I don't use foil balls as I want to see the clearance across the entire dome - side-to-side and top-to-bottom. So I use modeling clay and put two 1/8" or so beads/strips to cover the top of the piston -- one from 12 o'clock to 6 o'clock, the other from 9 o'clock to 3 o'clock.

Steps:

1) Clean all oil/crap from top of piston (I use acetone or lacquer thinner). Then, rub a tinny bit of oil on the chamber/dome area of the pistons. (This keeps the modeling clay from sticking).

2) Clean chambers - the same way. (put no oil on these - so clay will stick)

3) Put a head gasket on dry and fasten the heads down as you noted

4) The gasket manufacturer should be able to tell you the compressed gasket thickness - so use THEIR figure in determining the final gasket thickness. I've not seen these gaskets compress anywhere near .010. Usually the final thickness is around .050 to .052 for stock style gaskets.

5) Slowly/carefully take the head back off and use an XActo knife to gently cut down the middle of both strips of clay - remove one side of each strip to see the thickness across the entire dome (all directions and areas). This gives you a really good idea as to how close you are to the head - and "where". You can "measure" the thickness of the clay using a mic - I have a little 1" depth mic that I use. Obviously you have to be gentle with the modeling clay.

6) If the gasket makers "compressed height" is smaller than what you measure out of the box, then use the difference between a new gasket and their compressed thickness to determine actual gasket "squish". Subtract this from your clay numbers.

7) Pay attention to the piston dome shape as it relates to the head chamber shape - as I noted, sometimes the piston domes are NOT the same shape as the head domes - so consider this in how you end up with your final squish number determination. You'll use the SMALLEST thickness of the clay in your calculations - could be mid-way on the dome, could be up at the top . . . just pay close attention to the clay strips and how consistent (or not) their thickness is.

Good luck!
B&S

 

[Bored&Stroked]

Here are some pictures:

Notice that I also clay the tops of the valve reliefs in the heads - this is there the valves are the closest.

 

[Ol' Ron]

The evolution of installing heads on a flathead is more complex, than a woman's mind. In the "Beginning". We slaped them on torqued them to 60/70 lbs and went racing. When we started using racing cam shafts and milled heads, we found that pistons hit the heads ar reva and the heads leaked, torque then to 80. Learning can be expensive. stripped blocks and Heli coils later?? It took awhile to realize that over torquing the heads was a bad idea, one shop used a torque plate for honing the SBC, so whynot the flatheads. Most of us used Jahnns pistons with .005/6" clearance ( Made from Lead???) Now we used .076/.100 piston clearance. But torquing the heads was still amistory. Back to 50 llbs. Problem solved.. So much for the learning curve, I have no idea who came up with all this?With the low RPM's of the street engines and the light Forged and Egge 3 ring pistons, we can tighten up the piston to head clearance.
THis doesn't address the long term installation of aluminum heads on a cast iron block. When I first started rebuilding Flatheads I began repairing used heads to reduce the price of the builds. I checked the fire ring of the heads, milled them flat. Bead blasted them and filled the corrosion areas with Devcon F and later JB weld. We had an aluminum spray sealant in the beginning, but later versions were just aluminum paint. Since then I use copper coat. However I don't think this will help the long term installation of these heads, but a new method maybe around the corner. Paint the heads with a coat of Latex paint. Install gasket with what ever sealant you want, and bolt the heads down with cadmium coated bolts (with hardened washers) . Torque to 45 lba for 3 or mor heat cycles. Untill there is no movement. You might wonder if this is enough?? I did. after the hydro engine made a run at over 60mph, a recheck of the head bolts gave little movement. The Evolution continues, tune in next year.

 

[Ol' Ron]

Mtt

 

[Bored&Stroked]

Yeah Ron - there are more stories, methods and claims about exactly HOW to do anything on a flathead . . . many of them old wives tales.

I've found so many of them were just passed on as flathead "facts" - when few of the people passing them on had actually experienced what they were talking about. You start to figure that out about the time you start asking "Why?" and "How do you know?" - the resulting answers got pretty thin (in many cases).

Lots of myths, lots of "hot tips" . . . but also lots of experimentation (whether intentional or not). I wish I'd started writing down all the stories I've heard over the years - the resulting BOOK would be big and terribly inconsistent! LOL

Lots of ways to skin the flathead cat . . . and lots of "skinners" out there willing to tell you exactly how . . . .

Building a Flathead is exactly the same as using "Google" to look up something. You'll get lots of answers to your questions - in the end it is up to YOU to decide which ones you want to believe and/or actually apply to your own specific engine.

B&S

 

[tubman]

Dale, I'm kinda surprised at your post. It seems to me that just about everybody who contributed said about the same thing; no sealer, check the plug length, several torque cycles to 45, check the piston to head clearance etc., etc., etc.

 

[Bored&Stroked]

Dale, I'm kinda surprised at your post. It seems to me that just about everybody who contributed said about the same thing; no sealer, check the plug length, several torque cycles to 45, check the piston to head clearance etc., etc., etc.

In my post above, I was just commenting on how it is easy to learn something on the internet, but then one has to determine how to use that information, make choices - especially as it relates to what do you do first, next, etc.. It was in reply to the "evolution" of his methods that Ol' Ron was referring too.

I learned the basics early on (at about 15 years old) - then I learned the details over the next 40 years - and I'm still learning! (Sometimes due to the hard lessons learned when things didn't work as I thought they were going too - or because I only knew part of the story as the information I received was partially correct or I didn't comprehend the pitfalls).

Example: If one has never really checked piston to head clearance on a flathead - how do they know what to do . . . and that what they measure one place might not be the whole story?

Or that what they measure on one side of the engine - might be very different on the other side of the engine (different deck heights).

Or that their head gaskets are not going to compress much . . . so the math matters.

Even with all the help and mentors I've been lucky enough to have - there is still a lot of individual learning gained with hard earned experience that only comes with time.

Okay - I'm even putting myself to sleep!

 

[frnkeore]

I was a mechanic for 8 years and then I became a machinist in 1973.

Even as a mechanic I didn't realized how important that dimensions are! You buy stuff and you expect it to fit, what ever your building but, if you do not know what the dimensions are, you really don't know what your doing.

Heads, for the flat heads, are good example. Especially used heads! heads are hard to measure accurately but, you need to know at least two things. First the depth of the valve pocket, to make sure you have enough vertical clearance for a after market cam. Not so hard to do if, you have a depth mic and know how to use it. Second, they need to be CCed, w/o that, your not going to have any idea what your CR is. You of course need those figures for all 8 combustion chambers.

For CR, there are a few more things that you have to know:

1. The thickness of your compressed head gasket. This can vary from about .040 to .070.

2. Your deck clearance.

3. If you have domed pistons, the volume of the dome.

4. And the least important, the volume of the area from the top of the piston, down to the first ring. You can do that with math. Measure the diameter of the piston top and the depth to the first ring, then subtract from the same amount of bore diameter. FH's can vary a lot in this dimension. This won't amount to .10/1 CR difference.

5. There is also a small amount of volume, around the valves, themselves and if the block is relieved, there is that to deal with, it can amount to much more than #4. For that, you would have to put a tight fitting sleeve in the bore, even with the deck and CC that area.

If you just slap on a set of "8/1" heads, your really not going to know what you have.